It used to be reasonable to assume that driving to a particular city was cheaper than flying there. But that assumption is no longer usually true because of rising fuel costs, cheap flights, and other factors. Here to help you find out whether driving or flying will be cheaper for a particular trip is a web service called the “Fly or Drive” calculator by BeFrugal.

Fly or Drive Calculator is a free to use web service that helps you determine the cost of driving and flying from a particular city to another. You can specify your departure and arrival cities, vehicle type, number of travellers, start and return dates, and whether or not your trip will be a return one. From its default settings, the web tool generates its time and cost predictions and shows them to you.

In order to change the driving and flying cost factors you can access individual settings and modify them.

Ah, yes, just brilliant: "This service only supports locations within the continental United States. Your location Houston, TX, USA does not appear to be in the continental United States." [Added bonus: we will now crash your browser.]